diff --git a/main.c b/main.c
index d3cfd3b..a9aaf10 100644
--- a/main.c
+++ b/main.c
@@ -15,6 +15,7 @@ int conf_width = 1920;
 int conf_height = 1080;
 int conf_iomode = IOM_MMAP;
 int conf_samples = 25;
+float conf_filter = 0.1;
 int conf_rotate = 0;
 Rect conf_rect = { .x = 315, .y = 0, .w = 70, .h = 1910 };
 char conf_outdate[LEN_FILENAME];
@@ -38,6 +39,7 @@ void help() {
 	printf ("\t-debug OUTDIR           debug files output dir\n");
 	printf ("\t-ioread                 use read instead of mmap\n");
 	printf ("\t-samples NUM            samples to read\n");
+	printf ("\t-filter NUM             filter over NUM lines for detection\n");
 	printf ("\t-rect X,Y,W,H           part of the screen to search for the level\n");
 	printf ("\t-rotate DEG             rotate image by 0,90,180,270\n");
 	printf ("\t-help                   display this help\n");
@@ -74,6 +76,10 @@ int main(int argc, char **argv) {
 			i++;
 			conf_samples = atoi (argv[i]);
 		}
+		else if (strcmp(argv[i], "-filter") == 0){
+			i++;
+			conf_filter = 1.0/(float)atoi (argv[i]);
+		}
 		else if (strcmp(argv[i], "-debug") == 0){
 			i++;
 			strncpy (conf_debugout, argv[i], LEN_FILENAME-1);
@@ -176,12 +182,15 @@ int detect_level(ImageFloat *imgf) {
 	int y, x, level;
 	float v = 0.0, vmin, vmax;
 	FILE * outfile;
-	float deltamin = 0, deltamax = 0;
-	int deltamin_y = 0, deltamax_y = 0;
+	float deltamin = 0;
+	float deltamax = 0;
+	int deltamin_y = 0;
+	int deltamax_y = 0;
 	
 	if (imgf == NULL) return -1;
 	
-	float *deltas = malloc(sizeof(float) * imgf->h);
+	float *deltas  = malloc(sizeof(float) * imgf->h);  // deltas
+	float *deltasf = malloc(sizeof(float) * imgf->h);  // filtered deltas
 	if (deltas == NULL) {
 		printf ("%s:%d could not allocate memory. Error:%s\n", __FILE__, __LINE__, strerror(errno));
 		return -1;
@@ -214,33 +223,40 @@ int detect_level(ImageFloat *imgf) {
 
 	// generate average and delta
 	level = 0;
-	float delta = 0.0;
+	float delta = 0.0, deltaf = 0.0;
 	for (y = 0; y < imgf->h; y++) {
 		// average
 		v = 0.0;
 		for (x = 0; x < imgf->w; x++) v += imgf->data[x + (y) * imgf->w];
-		v /= (float)imgf->h;
+		v /= (float)imgf->w;
 
 		// output
 		for (x = 0; x < outavg_with; x++) imgf->data[x + (y) * imgf->w] = v;
 
 		// delta
-		if (y > 0) delta = imgf->data[0 + y * imgf->w] - imgf->data[0 + (y-1) * imgf->w];
+		if (y > 0) {
+	        	delta = imgf->data[0 + y * imgf->w] - imgf->data[0 + (y-1) * imgf->w];
+			deltaf = deltasf[y-1] * (1.0-conf_filter) + delta * conf_filter;
+	        }
 		else {
+		        delta = 0.0;
 			deltamin_y = 0;
 			deltamax_y = 0;
 			deltamin = delta;
 			deltamax = delta;
+			deltas[0] = delta;
+			deltasf[0] = delta;
 		}
-		if (deltamin > delta) {
-			deltamin = delta;
+		if (deltamin > deltaf) {
+			deltamin = deltaf;
 			deltamin_y = y;
 		}
-		if (deltamax > delta) {
-			deltamax = delta;
+		if (deltamax > deltaf) {
+			deltamax = deltaf;
 			deltamax_y = y;
 		}
-		deltas[y] = delta;
+	       	deltas[y] = delta;
+	       	deltasf[y] = deltaf;
 	}
 
 	// debugging write output
@@ -252,7 +268,7 @@ int detect_level(ImageFloat *imgf) {
 			exit(1);
 		}
 		for (y = 0; y < imgf->h; y++) {
-			fprintf(outfile, "%05d\t%f\t%f\n", y, imgf->data[y * imgf->w], deltas[y]);
+			fprintf(outfile, "%05d\t%f\t%f\t%f\n", y, imgf->data[y * imgf->w], deltas[y], deltasf[y]);
 		}
 		fclose (outfile);
 	}
@@ -262,6 +278,7 @@ int detect_level(ImageFloat *imgf) {
 	level = deltamin_y;
 
 	free(deltas);
+	free(deltasf);
 	return level;
 };